Windows Slideshow Gadget Enhance

editing Slideshow Gadget file (Win7). Unfortunately, I've no coding experience so that's why I can't find solution for it myself. What I've dreamed for is slideshow on my desktop where I can see motivational pictures that would change once per 30 mins. Unfortunately windows gadget doesn't have such option (5 mins max) and it is too small for my needs. I tried to edit file by myself but I couldn't recieve results I wanted.

#1 when I tried to add 30 mins option in scroll menu the program wouldn't even start.I changed this:

var pictureArray= new Array();
var selectArray= new Array();
var slideTimeArray= new Array(
["5 " + L_SECONDS_TEXT, 5],
["10 " + L_SECONDS_TEXT, 10],
["15 " + L_SECONDS_TEXT, 15],
["30 " + L_SECONDS_TEXT, 30],
["1 " + L_MINUTE_TEXT, 60],
["2 " + L_MINUTES_TEXT, 120],
["5 " + L_MINUTES_TEXT, 300]);

[code]....

#2 When I tried to change size of slideshow it wouldn't fit in border -->I changed this

var maxDockedWidth= 120;
var maxDockedHeight= 90;
var maxUndockedWidth= 320;
var maxUndockedHeight = 240;

[code]....

If the size of slideshow could be 534x333 px that would be perfect!